Flashcards in Heavy Metals Deck (22):
potential routes of exposure to heavy metals?
what does LD50 stand for?
median lethal dose
causes death in 50% of the group given toxic substance
the lower the LD50= THE MORE TOXIC IT IS
five mechanisms of toxicity for heavy metals?
1. enzyme/cofactor inhibition or potentiation
2. disruption of membrane and other transport processes
3. disruption of mitochondrial function--> fatigue
4. decreased neuronal function and nerve conduction
5. bind sulfhydryl groups on proteins and a.a.s
how are people exposed to lead?
home: dust, paint, soil, imported remedies, some cosmetics, miniblinds, metal wicked candles
work: swallowing lead dust, contaminated air, contact, bring home from work
hobbies: car repair, artistic painting, stained glass, pottery glazing, soldering, target shooting, making bullets, slugs or fishing sinkers
drinking water: boiling does not get rid of!
products: computers, solder, pewter, ceramic glazers, jewelry, automotive batteries, imported or older pre-regulation products
environment: soil near roadways, businesses with lead
what population is at most risk for adverse effects dt lead exposure?
children living in older houses
PG women and the developing fetus
health effects of lead?
most excreted but that which is not can move between blood, soft tissues and mineralizing tissues
affects all organ systems
developmental: crosses placenta, neurological effects on kids
neuro: targets hippocampus, decreases ASA activity
endocrine: effects vit D levels, may alter thyroid fxn w/chronic exposure
cardio: increases risk of HTN
lead poisoning mechanism?
interferes w/heme synthesis by diminishing delta-ALA dehydratase activity= microcytic, hypochromic anemia w/basophilic stippling
ssxs of lead poisoning?
acute lead encephaloptahy
how to best test for lead levels in the body?
adults: should be less than 20 mcg/dL
children: should be less than 5 mcg/dL
how do you manage lead toxicity?
remove exposure to toxic substances
chelation: if very high blood levels
eat diet high in calcium and iron as these displace lead
major source of mercury poisoning for the population at large?
inhalation of elemental mercury volatilized from dental amalgams
3 forms of mercury
organic: methylmercury, ethylmercury
inorganic: mercuric chloride, mercuric sulfide
where do you find methylmercury? what can it cause?
find when person has eaten large amounts of fish over weeks to months - 95% comes from food
damages nervous system, infants can be born with cerebral palsy --> all because can cross the BBB
where do we get exposure to ethylmercury from?
break down of thimerosal
excreted from body more quickly than methyl
where are inorganic mercury forms mostly found?
skin lightening creams
should be less than 5 microg/L
predominant commercial use of cadmium?
airborne cadmium exposure occurs via what substances? can also be found where
burning fossil fuels
incineration of multiple waste materials
zinc, lead, copper or smelters
cigarette smoke inhalation
can also be found in the soil- has a high rate of transfer to plants such as cereal grains, wheat, rice, potatoes and seeds
health effects of cadmium exposure?
can lead to iron deficiency
decreased olfactory fxn
accumulates in liver and KDs (irreversible proteinuria and progressive reduction in GFR) where it binds to metallothionein
can result in painful osteomalacia or osteoporosis
associated with lung CA
reproductive and teratogenic effects, increase in endometrial CA, may have a role in prostate CA
historical uses of arsenic?
medicines, cosmetic lighteners, paint pigments, wood preservation
two forms of arsenic? which is more toxic?
organic: excreted quickly via urine
inorganic is MUCH MORE toxic- well absorbed from GI tract, come from water, cigarette smoke and poultry
health effects of inorganic arsenic on the body?
inhibition of numerous enzymes, substitution in phosphate metabolism, interference in signal transduction pathways, alters gene expression